Among X-ray detectors used in X-ray computed tomography (CT) apparatuses are those provided with a data acquisition system (DAS). For example, a general X-ray detector with DAS amplifies analog signals based on detected X-rays in units of detector elements. After that, the X-ray detector converts the analog signals into digital signals, and controls the transmission of the digital signals in units of modules consisting of a number of detector elements. On this occasion, inside the X-ray detector, data is transferred via wire using a flexible printed circuit (FPC), a connector, and the like.